Automatic flyback board for LowZ (low impedance injectors).
Only useful in a setup with low-Z injectors (installed now or possibly later): allows PWM-ing which makes series power resistors unnecessary and makes injector close faster (=better control, easier to tune idle, better toleration of injector-opening variances between all cylinders).
The 4 channels are: inj-A,B,C,D (1,2,3,4): EC36/7, EC36/19, EC36/8, EC36/20 respectively. If number of injectors > 4 then the 8-channel version must be used.
Genboard v3.x supports injector PWM-ing:
After about 1msec of full (14V) drive, PWM-ing (35..50% duty is most common) is the coolest method for driving low-impedance injectors (results in less heat in injector drivers).
This automatic flyback board provides the required low voltage flyback while PWM-ing is active, and high voltage flyback to make injectors turn off faster after PWM-ing is over (for the best of both worlds).
Effectively, instead of low-voltage flyback all the time this results in faster injector switchoff and therefore more predictable fuel-delivery between cycles and between different injectors (different injectors have slightly different closing characteristics, even from the very same manufacturing batch - even if measured+grouped, injector closing characteristics changes a bit during operation).
Please look at the picture (click for bigger).
The low-Z extension "daughterboard" is normally mounted on top of v3 to injector FET mid-pin outputs (for much easier mounting, extra pads are available on the mainboard since v3.8).
On top of these 4 or 8 connections (depending on 4/8channel) to be made between daughterboard and mainboard, there is only one extra pad to wire: in the middle of the low-Z extension board, the "flyrail pad" which is connected to the (non-stripe-marked leg) anode of the big 1k5E / 30V unidir transient-protection diode:
wire this "flyrail pad" to the injector common +12V (which goes to all injectors), normally via EC36/23.
Note that you might want to remove the big 1k5E / 30V unidir transient-protection diode from the mainboard before installing the daughterboard: the low-Z has similar big 1k5E / 30V unidir transient-protection diode, when properly installed, the (non-stripe-marked leg) anode "sinking current" to the EC36/23 that one can (should) verify.
(The transient diode on the mainboard could stay, only justification to remove is for mechanical reasons for easier/closer mounting of the daughterboard).
With highZ injectors or low-Z injectors with series resistors, PWM-ing should be configured off (100%, 25.5msec) than low-Z extension kit does not give advantage (but does not hurt either).
If PWM-ing is not required, the default 30V "high voltage flyback" is a cheaper solution with same effect (but than PWM-ing must be disabled to avoid damage).